1. Field of the Invention
The present invention relates to a video image processing apparatus and a video image processing method.
2. Description of the Related Art
Motion-adaptive IP (interlaced-to-progressive) conversion is a method for converting interlaced video image signals to progressive video image signals, by interpolation. In such a method, video image motion (motion information) is detected at an interpolation pixel generation position, and in accordance with motion information, there is adaptively switched between generation of an intra-field interpolation pixel, and an inter-field interpolation pixel, as interpolation pixels.
In motion-adaptive IP conversion, an interpolation pixel is generated at a position determined to “have motion”, by using pixels that are adjacent, in a vertical direction, to that position, within one same field. As a result, raggedness known as “jaggies” occurs at edge portions in an oblique direction (oblique edge portions), which significantly impairs video image quality (image quality).
Methods proposed as techniques for suppressing the occurrence of jaggies involve detecting an oblique edge portion, on the basis of pixel information of an inputted interlaced video image signal, and generating an interpolation pixel for the oblique edge portion, using pixels in accordance with the inclination angle (edge direction) of the oblique edge portion.
For instance, a method has been proposed wherein, upon generation of an interpolation pixel that is positioned between a determination block and a reference block that resembles the determination block, the interpolation pixel is generated using at least any one pixel from among pixels in the determination block and the reference block (Japanese Patent Application Publication No. 2005-303999).
In the abovementioned method, however, image quality is significantly impaired if the inclination angle is misdetected.
Methods for determining the certainty of the inclination angle have been proposed (for instance, Japanese Patent Application Publication No. 2005-341346), that involve discriminating complexity in a horizontal direction of each line on the basis of images at lines that are adjacent, in a vertical direction, to an interpolation pixel generation position, and determining whether the interpolation pixel generation position is a position at which interpolation is to be performed for an oblique direction.
In the above-described conventional technologies, however, misdetection of oblique edge portions occurs, depending on the content of the input image, upon detection of the oblique edge portions on the basis of interlaced video image signals. For instance, a periodic pattern portion in the horizontal direction is likely to be misdetected as an thin line portion having a shallow inclination angle, or as separate thin oblique line portion (i.e. oblique edge portion), and vice-versa.